An Investigation into the effect of varying enzyme concentration on the rate of an enzyme controlled reaction.

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An Investigation into the effect of varying enzyme concentration on the rate of an enzyme controlled reaction

The aim of my experiment is to see whether there is a relationship between the enzyme concentration and the initial rate of the reaction. The reaction involves catalase breaking down hydrogen peroxide, which is the substrate. The enzyme is yeast.

This is the reaction:        2H2O2(l)      2H20(l) + O2(g)

Background Knowledge


Enzymes are biological catalysts, which are made up from groups of protein molecule. An enzyme has an active site, which has a unique shape (lock) into which only a substrate of the exact same unique shape (key) can fit. When this substrate links into the active site it forms something called an enzyme-substrate complex. Catalysts are substances, which speed up the rate of a reaction, but do not get used up themselves.

Enzymes will denature in certain conditions. These conditions are high temperatures and high levels of pH. The bonds that hold enzymes together are weak and so are easily broken by these factors. If these bonds are broken the enzyme, along with the active site, gets deformed. This is called a denatured enzyme. There are two types of enzymes, Extracellular Enzymes and Intracellular Enzymes. Extracellular enzymes are enzymes that can control reactions, which happen outside cells. Intracellular enzymes control reactions that happen inside cells.

        Catalase is the enzymes used in my experiment. It is an extracellular enzyme. In this experiment it is used to break down the hydrogen peroxide in cells.

The collision theory is another theory to explain enzyme-substrate interactions. It states that enzyme and substrates (or reactants) must collide with each other in order to react. They don’t have to all be match up before a reaction takes place.

The temperature affects this theory as the temperature increases movement of the particles (enzymes and substrates), known as the kinetic theory. This increases the chances of them hitting each other. Between 5º and 40ºC the rate of reaction doubles for every 10ºC rise in the temperature. The optimum temperature for enzymes to work at is human body temperature, which is around 37ºC. If the conditions are hotter than 40ºC then the rate of reaction decreases because the high temperatures cause the enzymes to denature. When they denature, it means that the heat has damaged the molecule so it changes shape and so the ‘key’ can no longer fit in the ‘lock’. If the conditions get below 35ºC then the rate of reaction slows, as the enzymes cannot move fast enough to collide with the substrate molecules. At really high temperatures the enzyme will break and will never be able to be used again.

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Bibliography

To find my background information I used:

  • My AQA biology coordinated award book
  • My notes from class

 

I have to keep the pH and temperatures the same throughout the experiment otherwise the enzymes will denature. Extreme pH level also makes the enzyme denature. Catalase has an optimum temperature of about 30ºC and an optimum pH of 7.

        

Identifying variables

Enzymes can be affected by the conditions they are in, these conditions are:

  • PH (must stay the same for this reaction)
  • Temperature (must stay the same, see above for details)
  • Enzyme concentration ...

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